Hydraulics

Just purchased a 4230. I am new to this size tractor and the hydraulics. It does have a front end loader that is not John Deere. The loader is connected to one of the hydraulic sets at the rear of the tractor (there are two sets). When a piece of equipment is hooked up, the cylinder bleeds down. This is true with the shredder or the plow. The front end loader does not bleed down even if the hoses are switched to the other set on the rear of the tractor. Now, since the controls for the front end loader are separate, could it be the controls on the tractor? Suggestions--help on how to diagnose and repair.

Thanks,